1. Field of the Invention
The present invention relates to a thermal assisted magnetic recording head that is provided with a temperature sensor.
2. Description of the Related Art
In order to increase the recording density of magnetic recording, a recording system has been known that allows to record stably to particles with a small diameter by increasing a magnetic anisotropy constant of a magnetic recording medium and at the same time allows to record easily by heating a region to be recorded locally so as to decrease coercive force of the magnetic recording medium. A magnetic head that performs recording using the above-described recording system is referred to as a thermal assisted magnetic recording head. Near-field light is preferably used to heat when a region on the magnetic recording medium that is to be heated is smaller than a wavelength of light.
U.S. Pat. No. 7,330,404 discloses a technology that matches an oscillation frequency of light with a resonant frequency of plasmon that is generated on a metallic scatterer by irradiating light to the metallic scatterer. However, because the metallic scatterer that is a near-field light generator deforms due to excessive heating, this method is not suited for practical use. As a technology that allows to prevent such excessive heating, U.S. Pat. No. 7,855,937 and U.S. Pat. No. 8,000,178 disclose a thermal assisted magnetic recording head that uses surface plasmon polariton coupling. The technology described in the above-mentioned specifications uses surface plasmon polariton (hereinafter, occasionally referred to also as “surface plasmon”) that is generated on a surface of a near-field light generator by evanescently coupling light propagating through a waveguide with the near-field light generator instead of irradiating the light directly to a plasmon antenna. The usage of the surface plasmon allows to suppress the excessive heating to the entire near-field light generator.
When heating of the magnetic recording medium is performed, the temperature of the thermal assisted magnetic recording head itself is increased. When the temperature of the thermal assisted magnetic recording head is increased, thermal expansion occurs, and a thermally-deformable air bearing surface (ABS) deforms such as to project toward the magnetic recording medium. When the thermal expansion is significant, the thermal assisted magnetic recording head may approach too much and collide to the magnetic recording medium, thereby causing damages. In order to control a flying height of the thermal assisted magnetic recording head from the magnetic recording medium such that the thermal assisted magnetic recording head does not approach too much to the magnetic recording medium due to thermal expansion, a temperature sensor made of a high resistance metal is provided in the thermal assisted magnetic recording head. The flying height of the thermal assisted magnetic recording head is controlled in correspondence with detection results of the temperature sensor, thereby preventing the collision with the magnetic recording medium.
In order to generate intense near-field light for performing high efficiency thermal assisted magnetic recording, intense coupling between the near-field light generator and propagation light is required. As a result, light penetrating into the inside of the near-field light generator that is made of a noble metal is intensified. The heat generation of the near-field light generator due to the light penetrating into the inside is not avoidable even when surface plasmon is used. For efficiently heating the magnetic recording medium and controlling the flying height of the thermal assisted magnetic recording head as described above, it is preferred to accurately determine the temperature of the thermal assisted magnetic recording head including the heat generation of the near-field light generator.
The objective of the present invention is to provide a thermal assisted magnetic recording head that accurately detects temperature with the temperature sensor and that has high heating efficiency of the magnetic recording medium by near-field light.